TEST: Better exception message if server sends wrong XML.

Summary

Better exception message if server sends wrong XML.

Focus

Exception for wrong XML: Is it easier to understand?

Test Environment

make unittest

Check List for the Author

Please, prepare your MR for a review. Be sure to write a summary and a focus and create gitlab comments for the reviewer. They should guide the reviewer through the changes, explain your changes and also point out open questions. For further good practices have a look at our review guidelines

• All automated tests pass (except integration tests)
• Reference related Issues: #100 (closed)
• Up-to-date CHANGELOG.md: not necessary?
• Add type hints in created/changed code
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there spezifications? Are they satisfied?

For further good practices have a look at our review guidelines.

unittests/data/list_in_value.xml

+<Record id="1002" description="A description of this example experiment.">
+  <Version id="945c6858819d2609a5475ee4df64571984acd039" head="true">
+    <Predecessor id="0df3cfe164fbafe9777f9356d0be2403890c54cd" />
+  </Version>
+  <Parent id="1001" name="Experiment" />
+  <Property datatype="SomeRecordType" id="1003" name="DepthTest" importance="FIX">
+    <Value>1004</Value>
+    <Value>1005</Value>
+  </Property>
+</Record>